This application incorporates by reference Taiwanese application Serial No. 89102365, filed on Feb. 11, 2000.
1. Field of the Invention
The invention relates in general to a scanning apparatus which is capable of locating the scanning starting point thereof, and more particularly to a scanning apparatus which is capable of locating the scanning starting point in an accurate and effective manner.
2. Description of the Related Art
In this multimedia age, scanners are becoming peripherals of wide usage. The users of scanners are interested in and demand a high quality and speed of scanning. For designing scanners meeting their needs, the operation of locating the starting point for scanning is concerned. A stepping motor conventionally drives the carriage of a scanner. When the carriage completes its scanning operation, it is required to return to its home position (i.e. the position where the carriage stays when idled and begins to move when starting to scan an object). However, this final operation may not always return the carriage to the same home position exactly. If the carriage is not returned to the home position exactly, it may result in the loss of part of the image of a scanned document or the capturing of the unnecessary image that is of no part of the scanned document. If the carriage can be accurately and effectively moved from the home position to the scanning starting point for document scanning, the errors mentioned above are avoided, resulting in a higher quality of scanning.
In the conventional approach to scanning a document, a predetermined reference point is first searched. The scanning starting point is then determined according to a predetermined displacement vector relation between the coordinates of the reference point and the scanning starting point. Once the scanning starting point is obtained, the scanning operations are able to start. There are two conventional methods for locating the scanning starting point as follows.
(a) Referring to FIG. 1, it illustrates the method for locating the scanning starting point by using the angle of the reflection region 12 on the calibration paper 10 as a reference point Q. This method is disclosed in the Taiwanese patent publication, serial No. 147499. The method utilizes the principle that the displacement vector relation between the reference point Q and the scanning starting point P is predetermined before leaving the factory. Thus, for obtaining the reference point Q, the carriage 11 slowly moves along the Y-axis and detects the difference of color between the reflection region 12 and the calibration paper 10. After obtaining the reference point Q, the scanning starting point P is determined according to the predetermined relative displacement. Therefore, the carriage can move to the scanning starting point P and begin scanning an object.
(b) Referring to FIG. 2, it illustrates the method for locating the scanning starting point by using the predefined mark 22 on the calibration paper 20, which is disclosed in the Taiwanese patent publication, serial No. 338868. It describes that when the carriage obtains the reference points Q1 and Q2 in a scanning line of the mark 22, the scanning starting point P is determined according to the predefined function of the coordinates of the two reference points and the mark 22, and the predetermined distance of a reference point Q and the scanning starting point P. Thus, the carriage begins to scan the object by the scanning starting point P.
However, in the conventional method illustrated in FIG. 1, since it is required that the carriage 11 slowly search for the reference point Q along the Y-axis and then moving to the scanning starting point P, the scanning speed per document is highly reduced. Moreover, in the manufacturing of the products according to the two conventional methods mentioned above, there may be errors in placing the reference point, resulting in a degradation of the quality of scanning. During the conventional method of printing a reflection region or a mark and installing a calibration paper, three errors may occur.
(1) Molding error. Since the calibration paper is of a certain thickness, a fillister is provided in the mold of the housing of the apparatus for the operator to stick the calibration paper. Thus, the error occurs in the process of making the mold.
(2) The error in the process of printing and cutting of the calibration paper. The calibration paper is made by printing individual reflection regions and marks onto a large piece of material before it is spliced into individual calibration papers. This may result in errors in printing and non-uniform size of the calibration papers due to inaccurate cutting.
(3) The error during sticking. This error occurs during sticking the calibration paper to the body of the scanning apparatus. The position that the calibration paper is stuck at may be inaccurate, resulting in errors when using the predetermined position and displacement vector relation.
When the carriage is moved for scanning an object, the unit of movement of it is in pixel (picture element) on the X- or Y-axis. For a common scanner with a resolution of 600 dpi (dot per inch), i.e. there are 600 picture elements per inch, the errors mentioned above are unacceptable. For scanner apparatus with higher resolution requirements, it is unacceptable and unavoidable.
It is therefore an object of the invention to provide a scanning apparatus capable of locating a scanning starting point. The scanning starting point is set for the scanning apparatus and no reference point is set. After locating the scanning starting point, the scanning apparatus begins to scan. In this way, it results in reduced time for locating the scanning starting point, a reduction of the errors described above, and enhancement of the accuracy in the scanning resolution and quality.
According to the object of the invention, it provides a scanning apparatus capable of locating a scanning starting point. The scanning apparatus includes a housing, a carriage, and a calibration paper. The housing includes a scanning platen for supporting a document to be scanned. The carriage, placed under the scanning platen, is for scanning objects supported by the scanning platen. The calibration paper is mounted on the scanning platen, adjoins one of the shorter sides of the scanning platen, and has a marked area. This marked area is defined by a set of functions and includes the scanning starting point for indicating the location of the document to be scanned on the scanning platen according to the scanning starting point. When the carriage is moved to a scanning line intersecting with the marked area, obtaining intersections of the carriage and the scanning line, the carriage locates the scanning starting point according to the intersections and the set of functions defining the marked area.